Air disperser for a spray dryer and a method for designing an air disperser

Disclosed is an air disperser (1) comprising an air inlet (2), a pipe (3) defining an air outlet area equipped with one or more atomizing means (4), an outer wall (7) and a space (8) defined by the pipe wall (9) and the outer wall (7) of the air disperser. The space has a plurality of guide vanes (10a-10l) positioned substantially vertically in the axial direction and substantially on the radii between the pipe wall and the outer wall of the air disperser. At least one (10e) of the guide vanes covers at least 90% of the full radius from the pipe wall in the direction towards the outer wall of the air disperser, and the rest of the guide vanes are distributed on radii along the circumference of the pipe.